Radiation source placement technology in brachytherapy is usually based on a system using ultrasound imaging or on a system using X-ray or computed tomography. Integrated into an applicator or a catheter, such a system for correct placement or localization is aimed to provide a correct radiation dose to tumorous tissue and to prevent excessive radiation of healthy tissue.
In treatments of e.g. prostate cancer, cervix cancer, tumors of the mouth and pharynx, lung cancer or liver cancer, there are two radiation therapy concepts commonly applied: the isotopic brachytherapy and the electronic brachytherapy. The main differences consist in the radiation energy which is considerably lower in electronic brachytherapy, providing radiation energy of e.g. max. 50 keV, (the radiation source can be turned off also) as well as in the treatment possibilities: in electronic brachytherapy, x-ray facilities as well as standard operation rooms might be used (short range and low mean energy of the radiation), which is not possible in isotopic brachytherapy, especially in so called high dose rate (HDR) brachytherapy. Generally, in isotopic brachytherapy, the radiation sources usually are millimeter sized seeds of radioactive isotopes, like e.g. the iridium isotope Ir-192, providing radiation energy in the range of 350 kV.
It is of common practice to spread out over time (or fractionate) a radiation therapy treatment. Brachytherapy is usually administered in a multiple fraction to allow normal cells time to recover. Tumor cells are generally less efficient in repair between fractions. The number of fractions and the dose to be administered during each fraction will depend on the treatment plan as well as the individual patient condition.
Usually, a plurality of applicator devices (or catheters) can be placed under real-time image guidance based on e.g. ultrasound (US) or x-ray, or it can be imaged after placement (based on e.g. computer tomographic CT techniques) or placed based on previously registered images, wherein a seed (or any radiation source) is pulled (where applicable robotically) through the applicator or through interstitially implanted catheters. The plurality of applicator devices are placed such that their respective tips are in contact with the tumor. This arrangement enables better control of the region to irradiate. Problems appear when it is required to displace the applicator, not least because one or several additionally required CT scans of the treatment area, or when the applicator moves between fractions of treatments, so that radiation exposure of the patient healthy tissue might be disadvantageously high, or alternatively that the radiation exposure of the tumor cell might be disadvantageously low. For example, in isotopic brachytherapy, imaging is done before each radiation session, wherein during the course of therapy e.g. about ten CT scans can be required to check if the applicator did not move since the last fraction.
An applicator device is known from US 2014/0005465. This application discloses a brachytherapy guidance system comprising at least one tissue sensor and an environment sensor for determining local tissue characteristics can be provided, e.g. based on spectroscopy measurements. By integrating tissue sensing functions in a brachytherapy system, the problems regarding low soft tissue contrast or missing information on the character of the irradiated tissue can be reduced or even mitigated.
It is a drawback of known interventional brachytherapy devices and systems that the quantity of radiation received by the tissue to radiate (the tumor), when irradiated by a radiation source, is difficult to assess and to monitor. Thus, the efficacy of the interventional brachytherapy is prone to mistakes.